Storm Review

The Friday Storm (I guess we can name it the Good Friday Storm of 2010) was one of the strongest late season windstorms in a while, with many locations experiencing gusts over 60 mph, and a few feeling true hurricane force winds. (Point of information: true hurricane winds require the sustained winds, averaged over two minutes, to exceed 74 mph). Such winds were achieved at Tatoosh Island yesterday. Here are some samples of max gusts (thanks to Scott Sistek of KOMO TV for collecting them)

• Tattoosh Island: 94 mph
• Lincoln City, Ore.: 78 mph
• Destruction Island: 78 mph
• Cape Disappointment: 74 mph
• Oak Harbor: 62 mph
• Bangor Sub Base: 62 mph
• Kirkland (waterfront): 62 mph
• Everett (Paine Field): 62 mph
• Bellingham: 61 mph
• Seattle (Alki Beach): 61 mph

Tens of thousands of homes lost power, including all of the San Juan Islands for a while.
Here is the hourly weather plot at Tatoosh Island. The the pressure dropped to 28.85 inches of mercury...around 976 mb as the low center moved NE in the close vicinity. And the maximum winds spiked after the lowest pressure. This is classic. Wind are not strong in the center of the low, but on its flanks where the pressure gradients (change in distance) are greatest.

The forecast the day before was close, but not perfect..here is the sea level pressure prediction made on Thursday. The low was displaced a small amount to the SE of the actual position and was not quite as deep as reality, but more than good enough to indicate a threat. National Weather Service warnings were highly accurate.


An interesting aspect of this event was the early snow. We had some moderately cool area over us and the evaporation and melting of precipitation forced the snow level down to the surface in some locations, particularly those over 500 ft and particularly over the SE side of the Olympics (Silverdale, Hood Canal Region). This location often experiences snow under strong SE flow--the air if forced to rise by the Olympics and evaporation and melting is favored there.

And snow is the big story now...1-1.5ft have fallen in the mountains from this event and another 1/2 feet will come today. Avalanche danger will be high in uncontrolled areas, but elsewhere this is a real opportunity for fine late season snow fun.